Cryogenic system

ABSTRACT

A cryosurgical system and method for supplying cryogen to a probe. The system including a container filled with cryogen and having bellows of a pump submerged within said cryogen. Conduits fluidly interconnect the bellows and a probe that is outside the container to permit the cryogen to be forced from the bellows to the probe upon activation of pump. A pressure relief valve is fluidly coupled to the conduits and positioned between the bellows and the probe. After initially forcing cryogen to the probe at a pressure that establishes a colligative-based sub-cooling of the liquid cryogen, the pressure relief valve is activated to lower the pressure of the cryogen to a running pressure.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/294,256, filed on May 31, 2001, the entire contents of which arehereby incorporated herein by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a cryogenic system. More specifically,illustrative embodiments of the present invention relate to a cryogenicsystem for use in cryosurgical procedures.

BACKGROUND

The distribution of boiling (liquid) cryogens, such as liquid nitrogen,is problematic due to the parasitic heat load provided by a cryosurgicaldevice's plumbing or transport circuit, which is maintained at ambienttemperature. Pre-cooling the plumbing circuit, even if adequatelyinsulated, causes two-phase flow (liquid-gas mixtures), cryogenboil-off, and choking flow due to gas expansion in the transportcircuit. As a result, target temperatures at the distal end of the flowpath (i.e., cryoprobe tip) are not reached for many minutes.

Some prior cryogenic systems and devices are disclosed in U.S. Pat. No.4,345,598 to Zobac et al.; U.S. Pat. No. 4,472,946 to Zwick; U.S. Pat.No. 4,860,545 to Zwick et al.; U.S. Pat. No. 4,946,460 to Merry et al.;U.S. Pat. No. 5,254,116 to Baust et al.; U.S. Pat. No. 5,257,977 toEshel; U.S. Pat. No. 5,334,181 to Rubinsky et al.; U.S. Pat. No.5,400,602 to Chang et al.; U.S. Pat. No. 5,573,532 to Chang et al.; andU.S. Pat. No. 5,916,212 to Baust et al., the entire contents of eachbeing hereby incorporated herein by reference thereto, respectively.

SUMMARY

The present invention can be embodied in a cryosurgical system,comprising a container having cryogen within the container; a pumphaving a piston submerged within the cryogen; a probe outside thecontainer for use in cryosurgical procedures; a system of conduitsfluidly interconnecting the piston and the probe permitting the cryogento be forced from the piston to the probe upon activation of the piston;and a pressure relief device fluidly coupled to the systems of conduitsand positioned between the bellows and the probe.

The present invention may also be embodied in a pump assembly for acryosurgical system, comprising a driving mechanism coupled to anelongated drive shaft; a bellows coupled to the drive shaft and adaptedto be submersed in cryogen, the bellows formed from metal; a one-wayinlet valve fluidly coupled to the bellows; and a one-way outlet valvefluidly coupled to the bellows.

The present invention may also be embodied in a method of deliveringcryogen to a surgical device, comprising providing a container havingcryogen within the container; providing a pump having a piston within acylinder and submerged within the cryogen; providing a surgicalinstrument outside the container for use in cryosurgical procedures;providing a system of conduits fluidly interconnecting the piston andthe surgical instrument permitting the cryogen to be forced from thepiston to the probe upon activation of the piston; providing a pressurerelief device fluidly coupled to the systems of conduits and positionedbetween the bellows and the probe; activating the piston to pull cryogenwithin the cylinder; activating the piston to push the cryogen from thecylinder to the surgical instrument at an initial predeterminedpressure.

Other aspects, features, and advantages of the present invention willbecome apparent from the following detailed description of theillustrated embodiments, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system in accordance with an embodiment of thepresent invention and includes a cross-sectional view through acontainer holding cryogen;

FIG. 2 is an enlarged, elevational view of the container of FIG. 1 andits contents;

FIG. 3 is an enlarged, top view of the assembly within the container ofFIG. 1;

FIG. 4 is a top view of a valve used in the system illustrated in FIGS.1-3;

FIG. 5 is an elevational view of the valve of FIG. 4;

FIG. 6 is a schematic view of the system illustrated in FIG. 1 andshowing the system as the bellows pulls cryogen within the cylinder;

FIG. 7 is a schematic view similar to FIG. 6 but showing the system asthe bellows initially pushes cryogen to the probe; and

FIG. 8 is a schematic view similar to FIGS. 6 and 7 but showing thesystem as the bellows pushes cryogen to the probe and with the pressurerelief valve activated to control the fluid pressure.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

FIGS. 1-8 illustrate a preferred embodiment of a cryogenic pump, system,and method according to the present invention. The system 10 providesinstantaneous sub-cooling of liquid cryogen 14, thereby creating acryogen state characterized by an excess capacity to absorb heat withoutboiling. By manipulating the pressure relationships in the plumbingcircuit 26, sub-cooled liquid 214 is transported to the distal cryoprobetip 130 in 1-20 seconds allowing near instantaneous freezing at theprobe tip 130. This rate of cooling is faster and the attainable lowtemperature is lower than comparable Joule-Thompson-based cryogenicdevices.

The illustrated system 10 includes a container or dewar 12 containingcryogen 14, such as liquid nitrogen. A support 16 is positioned withinthe container 12 and submerged within the cryogen 14. A pump 18 iscoupled to the container 12 such that the piston 56, illustrated in theform of a bellows, is also submerged within the cryogen 14. By way of aconduit system 26, the bellows 56 is fluidly coupled to an outputmanifold 20, a pressure release valve 22, and a surgical probe 24. Acontrol system 28 monitors the temperature of the probe tip 130 andadjusts the system components as necessary to maintain the desiredtemperature at probe tip 130.

The container 12 is of substantially conventional design, except that itis appropriately adapted to support pump 18. Pump 18 includes a lineardrive motor 52 mounted outside the container 12 and, preferably mountedto the top of the container 12. A drive shaft 54 extends down from themotor 52, through the cryogen 14 and couples to the bellows 56. Thebellows 56 is appropriately constructed to fit within a cylinder 58.Bellows 56 is preferably formed from stainless steel. Also, although thefigures illustrate a system 10 with two bellows 56, any appropriatenumber of bellow systems may be employed. The cylinder 58 has a one-wayinlet valve 60 coupled to an inlet conduit 62, and a one-way outletvalve 64 coupled to an outlet conduit. The cylinder 58 and bellows 56assembly is rigidly secured to the support 16 along with manifold 20.

Manifold 20 has an inlet conduit 80 fluidly coupled to the outlet valves64 of the bellows 56. Manifold 20 also has outlet conduits 82 fluidlycoupled to the probe 24. Although five outlet conduits 82 areillustrated it should be understood that the number of outlet conduits82 is dependent on the system requirements, and that more or feweroutlet conduits 82 may be used. The manifold 20 also has an outlet port84 for coupling with the pressure relief valve 22.

Pressure relief valve 22 is preferably mounted outside the container 12and is coupled to the manifold by inlet conduit 100. The valve 22 alsohas an outlet conduit that leads back into the cryogen 14 in container12 to return, to the container 12, the cryogen 14 that has been releasedfrom the conduit system 26 to lower the pressure as desired.

The surgical apparatus illustrated is shown as probe 24 with itscorresponding tip 130 and is intended to represent any appropriatecryosurgical device, including probe tips, such as those known in theprior art. Examples of prior art probes are disclosed in the patentsincorporated herein as set forth above.

Thus, the illustrated embodiment includes a reciprocating stainlesssteel bellows pump 18 that operates while submerged in liquid cryogen 14and that causes instantaneous sub-cooling of the liquid cryogen 14during the compression stroke of the bellows 56, thereby creating acryogen state characterized by an excess capacity to absorb heat withoutboiling. Further, by manipulating the pressure relationships in theplumbing circuit 26, sub-cooled liquid 214 is transported to the distalcryoprobe tip 130 in 1-20 seconds allowing near instantaneous freezingat the probe tip 130.

In the illustrated embodiment, one or more stainless steel bellows“pistons” 56 are driven by a surface mounted linear drive system 52capable of pressure regulation. The reciprocating action of each bellowspiston 56 a) sequentially produces a negative pressure to draw in liquidcryogen 14 on the fill stroke through a one-way check valve 60 and b)sequentially discharge liquid cryogen 214 at a prescribe pressureprofile out through a second one-way check valve 64 to a pressuremanifold 20 connected to the probe 24 plumbing circuitry. The preferred,prescribed profile is a range of between 250 pounds per square inch(psi) and 400 pounds per square inch (psi).

The pressure pulse profile establishes an initial high, transientpressure spike that causes a colligative-based sub-cooling of the liquidcryogen 14, which establishes a boiling point differential ofapproximately 30-40 degrees Celsius, thereby establishing an excesstemperature capacity (the level of temperature rise that can be allowedbefore boiling of the cryogen 14) supporting the instantaneousdistribution of sub-cooled cryogen 214 in the plumbing circuit 26.Following the transient pressure spike, pressure is reduced to a baselevel to sustain the desired rate of ice growth a the distal end of thecircuit, that is, at the probe 24. Conventional control systemtechnology can be employed in controlling the interaction between theprobe 24 and the pressure relief valve 22 and/or the pump 18, that is,in producing the control system 28

Pressure relief and control is provided by an appropriately designedpressure transducer-valve interface 22 outside the cryogen-containingdewar 12.

Thus, while the invention has been disclosed and described withreference with a limited number of embodiments, it will be apparent thatvariations and modifications may be made thereto without departure fromthe spirit and scope of the invention and various other modificationsmay occur to those skilled in the art. Therefore, the following claimsare intended to cover modifications, variations, and equivalentsthereof.

1. A cryosurgical system, comprising: a container having cryogen withinsaid container; a pump having a piston, said piston being submergedwithin said cryogen within said container; a probe outside the containerfor use in cryosurgical procedures; and, a system of conduits fluidlyinterconnecting said piston and said probe permitting said cryogen to beforced from said piston to said probe upon activation of said piston. 2.A system according to claim 1, wherein said cryogen is liquid nitrogen.3. A system according to claim 1, wherein said piston is a bellows.
 4. Apump assembly for a cryosurgical system, comprising: a driving mechanismcoupled to an elongated drive shaft; a bellows coupled to said driveshaft and adapted to be submersed in cryogen, said bellows formed frommetal; a one-way inlet valve fluidly coupled to said bellows; and aone-way outlet valve fluidly coupled to said bellows.
 5. A pump assemblyaccording to claim 4, further comprising: a supply manifold fluidlycoupled with said outlet valve, said supply and manifold having aplurality of ports.
 6. A method of delivering cryogen to a surgicaldevice, comprising: providing a container having cryogen within thecontainer; providing a pump having a piston within a cylinder, saidpiston being submerged within the cryogen within said container;providing a surgical instrument outside the container for use incryosurgical procedures; providing a system of conduits fluidlyinterconnecting the piston and the surgical device permitting thecryogen to be forced from the piston to the probe upon activation of thepiston; activating the piston to pull cryogen within the cylinder; and,activating the piston to pull the cryogen from the cylinder to thesurgical device at an initial predetermined pressure.
 7. A methodaccording to claim 6 wherein the activating the piston to push thecryogen from the cylinder to the surgical device at an initialpredetermined pressure includes pushing the cryogen to the surgicalinstrument at a pressure of between approximately 250 pounds per squareinch and approximately 400 pounds per square inch.
 8. A method accordingto claim 6 wherein after pushing the cryogen to the surgical device atthe initial predetermined pressure, activating the pressure releasedevice to decrease the pressure of the cryogen to a lower pressure thatis below the predetermined pressure.
 9. A system according to claim 1,further including a pressure relief device fluidly coupled to saidsystems of conduits and positioned between said pump and said probe. 10.A method according to claim 6, further including the step of: providinga pressure relief device fluidly coupled to the systems of conduits andpositioned between the bellows and the probe.